A traditional barrel comprises:                a barrel drum, which is a sort of cylindrical case comprising a bottom and side walls, the drum being provided with an exterior toothing to drive the train,        a barrel-arbor pivoting between bridge and plate and provided with a hook arranged on its core,        a strip-spring fixed by a first end to a countersink formed on the inner diameter of the side walls of the drum, and by a second end to the hook of the barrel-arbor, and        a lid closing the drum.        
The drum and the lid generally serve as a pivot for the barrel-arbor in order to stabilize the latter part. A ratchet is mounted integral with the barrel-arbor, generally square fit. It is driven by a winding device, manual or automatic, to cause the arbor to pivot and wind the barrel spring.
One skilled in the art knows that one of the main factors to improve the efficiency of a movement is the quality of the pivoting of the different elements and the weakness of the friction involved. This point is particularly essential at the level of the barrel, where the forces exerted are significant and where flaws in guiding of the arbor and drum can have non-negligible consequences for the power reserve.
Document CH 610178 proposes, with the goal of improving the pivot quality of the barrel, to mount it cantilevered using a ball bearing. The barrel-arbor is driven inside the inner ring of this bearing while the outer ring is fixed in a housing arranged in the plate. Furthermore, the drum is pivoted from the outside using runners with which it cooperates.
However, the presence of runners is particularly bothersome in terms of the bulk they create. Moreover, experience shows that the precision of the device proposed in the abovementioned document is not very satisfactory. The present invention aims not only to offset this drawback, but also to improve the pivoting of the barrel.